Many biological, physical, and social interactions have a particular dependence on where they take place. In living cells, protein movement between the nucleus and cytoplasm affects cellular response (e.g., MAPK proteins must be present in the nucleus to regulate their target genes).
Here we use recent developments from dynamical systems and chemical reaction network theory to identify and characterize the key-role of the spatial organization of eukaryotic cells in cellular information processing. In particular the existence of distinct compartments plays a pivotal role in whether a system is capable of multistationarity (multiple response states), and is thus directly linked to the amount of information that the signaling molecules can represent in the nucleus. Multistationarity provides a mechanism for switching between different response states in cell signaling systems and enables multiple outcomes for cellular-decision making. This is particularly important in MAPK phosphorylation systems, known to elicit bistability, and we discuss how the behavior of the MAPK system changes when considering the spatial dimension. We find that introducing species localization can alter the capacity for multistationarity and demonstrate that shuttling confers flexibility for and greater control of the emergence of an all-or-none response.